Obesity is an increasingly important problem for US children and adolescents. The prevalence of overweight among children and adolescents has increased from 5 percent to 16 percent in the past 30 years. It is a complicated disorder with biological, environmental, and behavioral correlates and often leads to serious medical and psychological complications. Although there have been major advances in our understanding of the physiologic, endocrine, and genetic bases of overweight, the disorder is ultimately caused by an imbalance between energy consumption and expenditure, factors that are mostly under behavioral control. Human eating behavior itself is a complex phenomenon that is poorly understood and has not been adequately studied in children and adolescents. Yet, eating behavior clearly contributes to the problem of overweight and is potentially modifiable. Our group has extensive experience in objectively characterizing eating behavior, meal-related perceptions, and meal-related hormones in adults with eating disorders and obesity. Our eating laboratory studies of bulimia nervosa have established that the eating behaviors of individuals with this disorder are objectively abnormal, and characterized by slowed gastric emptying and diminished post-prandial release of cholecystokinin. These findings have led to innovative treatment approaches now under examination. This R21 application is in response to PA-06-149 "Innovative and Exploratory Research in Digestive Diseases and Nutrition" and represents a novel and exploratory approach to adolescent obesity. We propose to develop an adolescent eating laboratory in order to examine the eating behavior and meal-related hormones of overweight adolescents before and after therapeutic interventions. This project is consistent with the Strategic Plan for NIH Obesity Research in that it bridges the gap between our knowledge about the biological underpinnings involved in food intake and an understanding of behavioral influences on human obesity. Our application represents a novel approach to understanding the mechanisms that underlie adolescent overweight and how these mechanisms are affected by therapeutic interventions. Ultimately, this approach should permit more rapid development and evaluation of treatments for overweight adolescents. The data from this R21 will form the basis for a later R01 application. Overweight in US children and adolescents is a serious public health problem. The etiology of the disorder is complex, but the condition is ultimately caused by an imbalance between energy consumption and expenditure, factors that are mostly under behavioral control, and thus potentially modifiable. The eating laboratory allows the careful measurement of eating behavior and meal-related hormones associated with hunger and fullness, which can be useful in examining pathways to this condition and understanding the mechanism of action of treatments for overweight adolescents. [unreadable] [unreadable] [unreadable]